<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <script>
        window.onload=function(){
            var bt=document.getElementsByTagName('button')[0];
            var bt1=document.getElementsByTagName('button')[1];
            var bt2=document.getElementsByTagName('button')[2];
            bt.onclick=function(){
                window.top.frames[2].history.go(-1);//previous
            };
            bt1.onclick=function(){
                window.top.frames[2].history.go(1);//next
            };
            bt2.onclick=function(){
                window.location.href="project/index1.html";//只改变浏览器窗口中frame1的页面
                // window.top.location.href="project/index1.html";//改变整个浏览器窗口页面
            }
        }
    </script>
</head>
<body>
<h1>frame1</h1>
<button>previous</button>
<button>next</button>
<button>跳转到index1</button>
</body>
</html>